Angiotensin II antagonists are used, for example, in the treatment of hypertension, anxiety, glaucoma and heart failure. A number of these compounds are characterized by a biphenyltetrazole moiety and can be represented by the following formula (I)

wherein Z is an optionally substituted heterocycle containing at least one nitrogen atom; or an amido residue.
Preferably, the residue Z has the following meanings, which identify specific angiotensin II antagonists:
2-butyl-4-chloro-5-hydroxymethyl-imidazol-1-yl (losartan);
2-ethoxy-7-carboxy-1H-benzimidazol-1-yl (candesartan);
2-butyl-1,3-diaza-spiro[4,4]non-1-en-4-on-3-yl (irbesartan); and
(S)—N-(1-carboxy-2-methylprop-1-yl)-N-pentanoylamino (valsartan).
Key intermediates for the preparation of compounds of formula (I) are 2-substituted phenyltetrazoles of formula (II)

in which R is hydrogen, a protecting group or a salifying group and Y is a —B(OR4)2 group, wherein each R4 is independently hydrogen or C1-C6 alkyl; or a ZnX group, wherein X is a halogen atom selected from chlorine, bromine and iodine.
A number of processes for the preparation of the compounds of formula (II) are known. For example, the process disclosed in U.S. Pat. No. 5,039,814 or in WO 93/10106 comprises the ortho-litiation of the phenyltetrazole and the subsequent transmetallation reaction. The main drawbacks of said process resides in the need to use an organo-lithium compound, i.e. a compound which requires specific safety precautions when used on an industrial scale, due to its high flammability and reactivity.
WO 99/01459 partly solves the problems deriving from the use of organo-lithium compounds by reacting a compound of formula (III)

in which R is as defined above,
with a Grignard reagent of formulaR1—MgX
in which R1 is C1-C6 alkyl or benzyl and X is as defined above;
in the presence of catalytic amounts of a secondary amine, which acts as a disaggregant of the Grignard reagent;
thereby obtaining a compound of formula (IV)

wherein R and X are as defined above. This compound is however hardly reactive and cannot be used as such in “cross-coupling” reactions for the preparation of compounds of formula (I). Therefore, this compound is subjected to a transmetallation reaction, according to known procedures, to obtain a compound of formula (II) as defined above, which is much more reactive. The use of a Grignard reagent, compared with an organo-lithium compound, is undoubtedly safer, but still potentially dangerous on an industrial scale and still requires specific procedures.
It is therefore evident that there is still need for an alternative process for the preparation of compounds of formula (II), in particular a process which does not require the use of Grignard reagents.